Mammalian Larynx Research Articles

Sound production biomechanics in three-spined toadfish and potential functional consequences of swim bladder morphology in the Batrachoididaea).

The relationship between sound complexity and the underlying morphology and physiology of the vocal organ anatomy is a fundamental component in the evolution of acoustic communication, particularly for fishes. Among vertebrates, the mammalian larynx and avian syrinx are the best-studied vocal organs, and their ability to produce complex vocalizations has been modeled. The range and complexity of the sounds in mammalian lineages have been attributed, in part, to the bilateral nature of the vocal anatomy. Similarly, we hypothesize that the bipartite swim bladder of some species of toadfish (family Batrachoididae) is responsible for complex nonlinear characters of the multiple call types that they can produce, supported by nerve transection experiments. Here, we develop a low-dimensional coupled-oscillator model of the mechanics underlying sound production by the two halves of the swim bladder of the three-spined toadfish, Batrachomoeus trispinosus. Our model was able to replicate the nonlinear structure of both courtship and agonistic sounds. The results provide essential support for the hypothesis that fishes and tetrapods have converged in an evolutionary innovation for complex acoustic signaling, namely, a relatively simple bipartite mechanism dependent on sonic muscles contracting around a gas filled structure.

Anatomical, Histological, and Electron Microscopic Structures of Syrinx in Male Budgerigars (Melopsittacus undulatus).

The syrinx is the main source for phonation in birds, its function is analogous to the mammalian larynx. Birds have both a larynx and a syrinx, but they use only the latter to vocalize. The objective of this work to give a detailed description of the anatomical, histological, and ultrastructural of syrinx in male budgerigars as a model of a passerine bird. The syrinx in the current study was to be found as a tracheobronchial type, it consists of cranial (tympanum) part and caudal (bronchosyringeal) part and, additionally, there are lateral vibrating membranes. The tympanum is formed of the last six tracheal rings, histologically its lamina epithelialis is a pseudostratified ciliated columnar epithelium with goblet cells and interrupted by intraepithelial glands. The secretory acini appear oval and lined by pyramidal secretory cells. The lamina propria–submucosa contain numerous blood capillaries, immune cells, and telocytes (TCs). The electron microscopic examination revealed numerous blood capillaries surrounded by fibroblasts and numerous immune cells, including mast cells and wandering leukocytes, within the tympanum mucosa. Hence, this study provides a detailed knowledge about the syrinx in male budgerigars.

Laryngeal inflammatory response to smoke and vape in a murine model

PurposeTo build a murine model for tobacco smoke and electronic cigarette vapor exposure to characterize the inflammatory and immune responses in the larynx. Materials and methodsIn this pilot study, twenty-four wild-type C57BL/6 mice were divided into four groups: smoke, vapor with nicotine, vapor without nicotine, and air only. Following daily exposure for 4 months, larynges were dissected and processed with cytokine detection arrays. Each laryngeal cytokine level between the four different groups was analyzed statistically by using statistical analysis software (SAS) to calculate the analysis of variance (ANOVA). ResultsIL-4 was the only cytokine found to achieve statistically significant different levels in this study, with elevated levels of IL-4 in the tobacco smoke and vapor with nicotine groups compared to the levels found in the vapor without nicotine and air only groups (p = 0.0418). While statistically non-significant, prominent findings revealed up-regulation of TGF-β2 and TGF-β3 in the smoke group, but near-normal levels of TGF-β2 and TGF-β3 and suppression of IL-10 in the vapor groups (p > 0.05). ConclusionThe potential utility of the murine model is established for studying the inflammatory and immune effects of tobacco smoke and vapor on the mammalian larynx. IL-4 levels in mice larynges were significantly elevated in the tobacco smoke and vapor with nicotine groups.

β-Catenin signaling is essential for mammalian larynx recanalization and the establishment of vocal fold progenitor cells.

Congenital laryngeal webs result from failure of vocal fold separation during development in utero Infants present with life-threatening respiratory problems at birth, and extensive lifelong difficulties in breathing and voicing. The molecular mechanisms that instruct vocal fold formation are rarely studied. Here, we show, for the first time, that conditional inactivation of the gene encoding β-catenin in the primitive laryngopharyngeal epithelium leads to failure in separation of the vocal folds, which approximates the gross phenotype of laryngeal webbing. These defects can be traced to a series of morphogenesis defects, including delayed fusion of the epithelial lamina and formation of the laryngeal cecum, failed separation of the larynx and esophagus with reduced and disorganized cartilages and muscles. Parallel to these morphogenesis defects, inactivation of β-catenin disrupts stratification of epithelial cells and establishment of p63+ basal progenitors. These findings provide the first line of evidence that links β-catenin function to the cell proliferation and progenitor establishment during larynx and vocal fold development.

Cilia-mediated Hedgehog signaling controls form and function in the mammalian larynx

Acoustic communication is fundamental to social interactions among animals, including humans. In fact, deficits in voice impair the quality of life for a large and diverse population of patients. Understanding the molecular genetic mechanisms of development and function in the vocal apparatus is thus an important challenge with relevance both to the basic biology of animal communication and to biomedicine. However, surprisingly little is known about the developmental biology of the mammalian larynx. Here, we used genetic fate mapping to chart the embryological origins of the tissues in the mouse larynx, and we describe the developmental etiology of laryngeal defects in mice with disruptions in cilia-mediated Hedgehog signaling. In addition, we show that mild laryngeal defects correlate with changes in the acoustic structure of vocalizations. Together, these data provide key new insights into the molecular genetics of form and function in the mammalian vocal apparatus.

Human Speech: A Restricted Use of the Mammalian Larynx

Speech has been hailed as unique to human evolution. Although the inventory of distinct sounds producible with vocal tract articulators is a great advantage in human oral communication, it is argued here that the larynx as a sound source in speech is limited in its range and capability because a low fundamental frequency is ideal for phonemic intelligibility and source-filter independence. Four existing data sets were combined to make an argument regarding exclusive use of the larynx for speech: (1) range of fundamental frequency, (2) laryngeal muscle activation, (3) vocal fold length in relation to sarcomere length of the major laryngeal muscles, and (4) vocal fold morphological development. Limited data support the notion that speech tends to produce a contracture of the larynx. The morphological design of the human vocal folds, like that of primates and other mammals, appears to be optimized for vocal communication over distances for which higher fundamental frequency, higher intensity, and fewer unvoiced segments are used. The positive message is that raising one's voice to call, shout, or sing, or executing pitch glides to stretch the vocal folds, can counteract this trend toward a contracted state.

Subglottal pressure and fundamental frequency control in contact calls of juvenile Alligator mississippiensis

SUMMARYVocalization is rare among non-avian reptiles, with the exception of the crocodilians, the sister taxon of birds. Crocodilians have a complex vocal repertoire. Their vocal and respiratory system is not well understood but appears to consist of a combination of features that are also found in the extremely vocal avian and mammalian taxa. Anatomical studies suggest that the alligator larynx is able to abduct and adduct the vocal folds, but not to elongate or shorten them, and is therefore lacking a key regulator of frequency, yet alligators can modulate fundamental frequency remarkably well. We investigated the morphological and physiological features of sound production in alligators. Vocal fold length scales isometrically across a wide range of alligator body sizes. The relationship between fundamental frequency and subglottal pressure is significant in some individuals at some isolated points, such as call onset and position of maximum fundamental frequency. The relationship is not consistent over large segments of the call. Fundamental frequency can change faster than expected by pressure changes alone, suggesting an active motor pattern controls frequency and is intrinsic to the larynx. We utilized a two-mass vocal fold model to test whether abduction and adduction could generate this motor pattern. The fine-tuned interplay between subglottal pressure and glottal adduction can achieve frequency modulations much larger than those resulting from subglottal pressure variations alone and of similar magnitude, as observed in alligator calls. We conclude that the alligator larynx represents a sound source with only two control parameters (subglottal pressure and vocal fold adduction) in contrast to the mammalian larynx in which three parameters can be altered to modulate frequency (subglottal pressure, vocal fold adduction and length/tension).

Nonlinear phenomena in northern mockingbird (Mimus polyglottos) vocalizations: Acoustics and physiology

The bird sound source (syrinx), like the mammalian larynx, has been discovered to behave as a nonlinear system of coupled oscillators. Modeling approaches as well as excised syrinx experiments show that the syrinx can be considered a nonlinear sound source. Until now, only few acoustic data were available showing to what extent a birdsong species’ vocal repertoire actually contains nonlinear phenomena, like subharmonics, frequency jumps, biphonation and deterministic chaos. The passerine syrinx, in contrast to the mammalian larynx, consists of two sound sources, one situated in each of the bronchi that are independently controlled. Bronchial airflow measurements showed that individual mockingbirds use each side of the syrinx independently. However, there are interactions of both sound sources, which have not yet been investigated acoustically/spectrographically. The present study shows how many of the spectrographically observed nonlinear phenomena are attributed to the interaction of the two sound sources, i.e., nonlinear phenomena, while both sound sources show positive airflow values, compared to single sound source utterances, i.e., positive flow through one sound source only. Nonlinear phenomena could be attributed to the interaction of the two sound sources (earlier referred to as ‘‘two-voice-phenomenon’’) but were also found to be produced by a single sound source.

Modeling the role of nonhuman vocal membranes in phonation.

Although the mammalian larynx exhibits little structural variation compared to sound-producing organs in other taxa (birds or insects), there are some morphological features which could lead to significant differences in acoustic functioning, such as air sacs and vocal membranes. The vocal membrane (or "vocal lip") is a thin upward extension of the vocal fold that is present in many bat and primate species. The vocal membrane was modeled as an additional geometrical element in a two-mass model of the larynx. It was found that vocal membranes of an optimal angle and length can substantially lower the subglottal pressure at which phonation is supported, thus increasing vocal efficiency, and that this effect is most pronounced at high frequencies. The implications of this finding are discussed for animals such as bats and primates which are able to produce loud, high-pitched calls. Modeling efforts such as this provide guidance for future empirical investigations of vocal membrane structure and function, can provide insight into the mechanisms of animal communication, and could potentially lead to better understanding of human clinical disorders such as sulcus vocalis.

Symmorphosis in relation to the relative dimensions of the glottic and tracheal area in the mammalian larynx.

A large number of non-human mammalian larynges have been studied in an attempt to relate body mass to maximum glottic and tracheal area in order to confirm symmorphism.

Developmental change in the position of the fetal human larynx.

The position of the mammalian larynx has been shown to be an important determinant in breathing, swallowing, and vocalizing patterns. While the growth of the adult human larynx has been studied extensively, detailed examination of fetal development has not been undertaken. Thus, crucial developmental change in the fetal period and the effects of this change on normal maturation are still unclear. This study has examined the development of the larynx and its topography during the fetal period. Thirty specimens were preserved in 10% buffered formaldehyde solution for a period of 6 weeks, after which mid-sagittal sections were performed. Fetal ages were calculated from femur diaphyseal lengths and ranged from 15 to 29 weeks. Direct measurements were taken to determine the growth and position of the larynx and trachea relative to the vertebral column and soft palate. Results show that the upper and lower levels of the larynx correspond to the basiocciput and the lower border of the third to upper border of the fourth cervical vertebrae, respectively. The epiglottic cartilage was present at 15 weeks. By 21 weeks, the epiglottis was well developed and in close palatal apposition. At 23 to 25 weeks, the epiglottis and soft palate were found to be in full contact. The acquisition of this contact may be related to fetal respiratory viability.

ヒトの聴覚喉頭反射

The mammalian larynx reacts promptly to external stimuli for protective and phonatory purposes. In particular, human speech has been thought to have an elaborate laryngeal control mechanism through the auditory system, although this has not yet been proved by empirical data. In the present study, the mechanism of laryngeal control through the auditory system was studied in terms of change in activity of the intrinsic laryngeal muscles.Healthy adults maintained phonation at a constant voice pitch while receiving repeated click-sound stimuli in both ears. The voice signal was transduced with a throat microphone and bandpass filtered to isolate the fundamental frequency (FO). Average values for about 40 recordings of this FO voltage at various click-sound stimuli were determind. The muscle activity of the larynx was recorded with bipolar wire electrodes inserted into the crico-thyroid muscles and/or the lateral crico-arytenoid muscles. The induced EMG (electromyographic)potentials were rectified, the average of about 80 values was calculated and the activity change in the intrinsic laryngeal muscles caused by the auditory stimulus was determined.1) A short-latency change in FO (about 50 msec) was noted in response to auditory stimulation.2) In most subjects who received sound stimulation of more than 90 dB during high pitch phonation, muscle activity increased with a steady latency, as shown by the electromyogram.3) The average time from the stimulus to the maximum amplitude of muscle activity was about 26 msec for the crico-thyroid muscle on both sides, about 45 msec for the right lateral crico-arytenoid muscle and about 47 msec for the left lateral cricoarytenoid muscle.

Twelfth Daniel C. Baker Jr memorial lecture: Victor Negus: 57 years later.

The three-dimensional morphology of the mammalian larynx was studied for 15 years. Using specimens obtained from a wide variety of sources, efforts were made to correlate structure with function and thus explain the variations in size and morphology seen in over 150 families of mammals.

Mechanisms for Communication

Animals use many different methods to produce communication signals even within a single sensory modality. For example, sounds may be produced by the passage of air through special organs as in the mammalian larynx and avian syrinx, by rubbing appendages against each other like insect legs and wings, and by striking objects in the environment as in woodpeckers.

Sphincters of the larynx.

THE PRODUCTION of sound is not the fundamental reason for the existence of the mammalian larynx, for there are mammals with larynges and no voices and, on the other hand, mammals with voices and no larynges. The two do not necessarily go together. Since this is true, what then is the basic purpose of the larynx? The larynx is actually a sphincter—a sphincter which physiologically isolates the respiratory tract below it from that above.* This is its primary purpose. There are, throughout the animal kingdom, no exceptions. The ability of the larynx in man to contribute to the production of sound is nothing more than a fortunate side-effect. There are, however, many types of larynges representing many types of sphincters. The human larynx is a three-tiered sphincter—the first being the true vocal cords; the second, the false vocal cords, and the third, the aryepiglottic sphincter. Some larynges, as described in